Development of gamma-aminobutyric acid–enriched germinated rice products

8

Development of gammaaminobutyric acid
enriched germinated rice products

Siming Zhao1, Junzhou Ding2 and Shanbai Xiong1 1 College of Food Sciences and Technology, Huazhong Agricultural University, Wuhan, P.R. China, 2Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, Urbana, IL, United States

Chapter Outline 8.1 Health benefits of gamma-aminobutyric acid and recommended dose

175

8.1.1 Function and health benefits 175 8.1.2 Recommended daily intake dose 176

8.2 Enhancement of gamma-aminobutyric acid content in germinating rice

177

8.2.1 The metabolism pathway of gamma-aminobutyric acid 177 8.2.2 The gamma-aminobutyric acid accumulation in germinating rice 177

8.3 Methods to enhance gamma-aminobutyric acid content in germinated rice 8.3.1 8.3.2 8.3.3 8.3.4

178

Soaking of rice seeds in nutrient solution 178 Enrichment via endogenous glutamate decarboxylase in germinated rice slurry 180 Enhancement of gamma-aminobutyric acid levels through fermentation 181 Enhancement of gamma-aminobutyric acid by environmental stresses stimulation 181

8.4 Development of gamma-aminobutyric acid-enriched rice products

182

8.4.1 Gamma-aminobutyric acid enriched rice-based staple foods 182 8.4.2 Gamma-aminobutyric acid enriched rice-based supplementary foods 184 8.4.3 Production and evaluation standard for gamma-aminobutyric acid
enriched germinated rice products 185 8.4.4 Future needs for gamma-aminobutyric acid
enriched germinated rice product development 185

References

8.1

187

Health benefits of gamma-aminobutyric acid and recommended dose

8.1.1 Function and health benefits γ-Aminobutyric acid (gamma-aminobutyric acid, GABA, C4H9NO2), a functional four-carbon nonproteinogenic amino acid, is widely present in plants and vertebrates (Shelp et al., 1999). Gamma-aminobutyric acid is the main inhibitory neurotransmitter in the vertebrate central nervous system (Owens and Kriegstein, 2002). Japanese researchers observed that oral GABA administration promoted relaxation Sprouted Grains. DOI: https://doi.org/10.1016/B978-0-12-811525-1.00008-7 Copyright © 2019 AACCI. Published by Elsevier Inc. in cooperation with AACC International. All rights reserved.

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in humans under stress (Abdou et al., 2006). Brain cells can release GABA in response to stimulation, including visual signal. While aging is generally known to degrade visual acuity in senescent humans and animals, application of GABA could counteract this, as some reports have showed that GABA improves visual function in old monkeys (Leventhal et al., 2003) and cats (Hensch and Stryker, 2004). Additionally, GABA has been recognized to influence several important physiological processes in higher animals when administered orally, such as blood pressure reduction (Inoue et al., 2003; Yoshimura et al., 2010) and regulation of hepatic cholesterol metabolism (Imam et al., 2014). Recent studies on functional foods indicated that GABA is widely considered as a functional nutrient with health benefits to humans (Palmer et al., 2012).

8.1.2 Recommended daily intake dose Gamma-aminobutyric acid occurs naturally in a variety of foods in our daily life, such as dehulled rice (Ng et al., 2013), tomatoes (Takayama and Ezura, 2015), and kimchi (Wu and Shah, 2015), to name a few. In recent years, GABA has received increasing attention as a health-promoting functional compound; numerous GABAenriched, plant-based food products have been commercialized in Japan and China. Gamma-aminobutyric acid is approved as a Generally Recognized as Safe (GRAS) substance by the US Food and Drug Administration (FDA) and has been used as a functional food component (FDA GRAS Notices, GRN No. 595, 2015). Manufactured GABA powders (see Chapter 3: Antioxidants in sprouts of grains) can be used as a drug and dietary supplement, which has been consumed in the United States as a dietary ingredient at proposed levels of up to 750 mg/serving (Pharma Foods International Co., Ltd, 2015). Gamma-aminobutyric acid
enriched foods have attracted considerable attention in the Japanese food industry over the past 20 years. In China, GABA became popular in the food ingredient market after being approved by the Ministry of Health P. R. China in 2009, with a recommended daily intake dose of no more than 500 mg (NHFPC, 2009). It is known that GABA synthesis in human and animal cells (Leventhal et al., 2003) and the blood-brain barrier permeability of GABA decrease gradually with ageing (Al-Sarraf, 2002). This is why GABA is recommended as a dietary supplement for aging populations, especially in high aging population countries, such as Japan and China. The dietary intake level of GABA from foods varies among different countries. Gammaaminobutyric acid is consumed in the United States at estimated levels of up to 136 mg/serving in various foods, and in Japan at levels of up to 280 mg/serving (Pharma Foods International Co., Ltd, 2015). No GABA-related side effect has been observed at these levels. Gamma-aminobutyric acid is well tolerated without symptoms of toxicity at doses of up to 1 g/kg body weight for up to 1 year for oral administration of GABA to rats and dogs (FDA GRAS Notices, GRN No. 595, 2015). A relatively new application of GABA is within the neuro-medical and pharmaceutical industries. In 2015, the FDA approved a new pharmaceutical, GABITRIL (tiagabine hydrochloride, NDA 020646/S-018), which was documented to

Development of gamma-aminobutyric acid
enriched germinated rice products

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enhance GABA in vitro experiments and prolong GABA-mediated inhibitory postsynaptic potentials in rat-derived hippocampal slices (Teva Pharmaceuticals, 2015).

8.2

Enhancement of gamma-aminobutyric acid content in germinating rice

8.2.1 The metabolism pathway of gamma-aminobutyric acid In higher plants including germinating rice, GABA is primarily metabolized via a short pathway called the GABA-shunt. The GABA-shunt includes two steps. The first step is the oxidation of α-ketoglutarate to succinate of the tricarboxylic acid (TCA) cycle via reactions catalyzed by glutamate decarboxylase (GAD) and GABA transaminase (GABA-T). The second step is the degradation pathway by succinic semialdehyde dehydrogenase (SSADH). Gamma-aminobutyric acid is synthesized directly from L-glutamate, and can be reversibly converted to succinic semialdehyde (SSA) by the action of GABA-T (Allan et al., 2009; Scott-Taggart et al., 1999; Shelp et al., 1999). The decarboxylation reaction of L-glutamate to GABA is dependent on the cofactor pyridoxal-50 -phosphate (PLP) or vitamin B6 (Diana et al., 2014).

8.2.2 The gamma-aminobutyric acid accumulation in germinating rice Rice is the seed of Oryza sativa (Asian rice) or Oryza glaberrima (African rice). As a common grain, rice is the most widely consumed human staple food. White rice can be cooked, or ground into flour for producing various rice-based products. Brown rice, black (purple) rice and red rice can be sprouted to increase nutrients levels and enhance flavor. Gamma-aminobutyric acid levels increase substantially in brown rice during germination (Moongngarm and Saetung, 2010; Patil and Khan, 2011), owing to the activated GAD and increased glutamate content during germination (Moongngarm and Saetung, 2010; Zhang et al., 2014). Furthermore, it is well known that increasing cytosolic levels of H1 can activate GAD (Crawford et al., 1994). The GABA level increases under acidic soaking conditions (Zhang et al., 2014). Moreover, the rice cultivar markedly influences GABA synthesis in germinated brown rice (Khwanchai et al., 2014; Ng et al., 2013). In recent years, enhancement of GABA in germinated rice has attracted more attention than other types of grains. Researchers have conducted extensive studies to breed new mutants, such as giant embryo mutant MH-Gel series (Zhang et al., 2007), and screen rice cultivars, such as high GABA black rice Heinuo series (Yao et al., 2008). Ding et al. (2016) identified and performed germination tests on a high GABA cultivar Oryza sativa L. subsp. indica “Heinuo,” a black glutinous landrace from more than 300 genotypes (Ding et al., 2016). The hulled and dehulled forms of the black Heinuo are shown in Fig. 8.1.

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Figure 8.1 The de-hulled (left) and hulled (right) forms of Black Heinuo rice Heinuo.

8.3

Methods to enhance gamma-aminobutyric acid content in germinated rice

Table 8.1 shows the published data on GABA concentrations in germinated rice products collected from test reports in China in 2013. In summary, researchers have studied several feasible methods for producing GABA-enriched rice products, such as soaking rice in a nutrient solution comprising L-glutamic acid (L-Glu)/sodium glutamate, PLP, and calcium chloride (CaCl2), post-germination enrichment using endogenous GAD, fermentation with GABA-producing microorganisms, and environmental stresses stimulation.

8.3.1 Soaking of rice seeds in nutrient solution The purpose of soaking or steeping of dehulled rice with water is to promote germination. During this process, protease, amylase, and GAD are activated, so GABA accumulation occurs. The temperature and time of both soaking and germination affect the GAD activity and GABA accumulation (Komatsuzaki et al., 2007). The GAD activity is regulated by the levels of L-Glu, Ca21, and H1; addition of L-Glu/ sodium glutamate; Ca21/calmodulin or reduction of cytosolic pH results in the stimulation of GAD activity (Scott-Taggart et al., 1999). Based on the studies of optimal germination conditions of brown rice, production equipment and production lines for producing germinated rice have been developed in the food industry, such as those designed by C&R Inc. (Nanjing, China). The production line comprises germination cans (fermentation vessels), water tanks, sterilization systems, drying equipment, and packaging equipment, as shown in Fig. 8.2.

Development of gamma-aminobutyric acid
enriched germinated rice products

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Table 8.1 A limited collection of documented GABA level in germinated rice Data source

Product

GABAa (mg/100 g)

Chinese Ministry of Agriculture, Food Quality Supervision and Testing Center, germinated rice sample

European germinated rice Japanese germinated rice Chinese germinated rice Chinese germinated rice Germinated brown rice powder Germinated rice Germinated rice

19.25

China Agricultural University Nanjing Agricultural University, patent CN, ZL200810056176.3 Nanjing Agricultural University Anhui Science and Technology University, patent CN ZL201110166784.1 Jiangsu Rainbow Food, patent CN ZL201110383466.0 Taipei Medical University South Central Forestry S&T University Hunan food quality supervision and testing Huazhong Agricultural University pilot scale, test by SGS in 2012 December

28.92 24.60 6.15
42.94 15
20 17
32 20
40

Germinated rice

2
12

Germinated rice in Taiwan Germinated brown rice Germinated rice germ Germinated red rice (12P19I-2) Germinated brown rice powder

40 12.52
75.34 16
142 50.5
58.1 111
320

a All the documented concentration of GABA is analyzed using HPLC method. Tables 8.1
8.3 are cited from the certification and appraisement of our the scientific research project report “Germinated Brown Rice Products with High GABA Content” certified by the Department of Science and Technology, Hubei, China, 2012, NO. 43073019, collaborated with Fu Wa Co., Ltd. (Jingzhou, Hubei, China).

Figure 8.2 Partial view of a basic commercial production line for sprouting rice germination in China. Photo source: http://www.fayame.com/product.html.

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8.3.2 Enrichment via endogenous glutamate decarboxylase in germinated rice slurry The activity of GAD increases considerably during germination (Khwanchai et al., 2014), and reaches a peak after 72 h of germination, as shown in the study with rice by Ding et al. (2011a). Therefore, it is practical to utilize the highly endogenous GAD activity from 72 h-germinated rice with slurry crushing and added calcium chloride and sodium glutamate to produce GABA. High GABA germinated rice slurry was obtained after crushing and in a post-germination extracellular enzymatic decarboxylation reaction for 4 h, as shown in a previous study (Ding et al., 2011b). Nutrient analysis results of brown rice and GABA-enriched germinated brown rice slurry are shown in Table 8.2. Fig. 8.3 shows GABA-enriched germinated rice flakes produced in a pilot study from the rice slurry using a drum dryer. Table 8.2 Comparison of nutrient levels between brown rice and GABA-enriched germinated brown rice slurry Nutrients (DB)

Unit (dry basis)

Brown rice

Germinated brown rice slurry

Changes (%)

GABA Crude protein Soluble protein Free amino acids Reduced sugar Total sugar Phytic acid

mg/100 g g/100 g mg/g μg/g mg/g g/100 g mg/g

19.71 6 0.34 14.96 6 0.11 6.22 6 0.11 122.32 6 1.92 3.08 6 0.02 83.06 6 0.17 7.42 6 0.22

1483.27 6 16.65 8.12 6 0.18 14.72 6 0.12 500.81 6 9.47 47.43 6 1.78 75.42 6 0.77 4.49 6 0.56

17425.47
45.72 1136.66 1309.43 11439.94
9.20
39.49

Figure 8.3 GABA-enriched germinated brown rice flakes from a pilot plant production line.

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Figure 8.4 General process of the fermentation-based method for GABA production.

8.3.3 Enhancement of gamma-aminobutyric acid levels through fermentation Gamma-aminobutyric acid
enriched foods have also been produced using GABAproducing microorganisms. Gamma-aminobutyric acid
producing lactic acid bacteria (LAB) are naturally present in acid-based fermented foods, such as Korean kimchi and Chinese pao-cai (Wu and Shah, 2015). Among them, Lactobacillus brevis species show the highest potential for producing large amounts of GABA. The biochemical properties of GAD in LAB were characterized in the 1990s (Nomura et al., 1999). There is a wide range of GABA-enriched food products fermented using LAB as the main GABA-producers, such as Italian cheeses, Burmese fermented fish products, yoghurt, and fermented milk and tea (Diana et al., 2014; Park and Oh, 2007). As reviewed by Wu and Shah (2015), many LAB strains producing high GABA quantities have been isolated, such as L. brevis NCL912 and L. brevis TCCC13007 from Chinese pickled vegetables (pao-cai,), L. brevis BH2, L. brevis K203, and L. brevis OPK-3 from Korean kimchi, L. brevis DPC6108 from Irish infant feces, Lactobacillus paracasei NFRI 7415 from Japanese fermented fish, and L. brevis CGMCC 1306 from Italian unpasteurized milk (Wu and Shah, 2015). The GAD activity varies among fermenting strains and therefore, their ability to produce GABA differs. An initial experiment showed that LAB has higher efficiency than yeast, demonstrated by maximum GABA accumulation at 60 h with LAB use, and 96 h with yeast use. The fermentation method for producing GABA rice products mainly focuses on the medium and bacterial cultivation for fermentation and a special starter culture. Zhao et al. (2015) developed a powder from specific single-strain and multi-strain starter cultures, such as Aspergillus Oryzae Lu-Niang 3.042, mixed with rice bran, sodium glutamate, calcium chloride, and Lactobacillus plantarum ZSM-002, Castro yeast ZSM-001; and Rhizopus ZSM-005 mixed with rice grains and rice germ (Patent CN104388514A). The process of the fermentation method to produce GABA is shown in Fig. 8.4.

8.3.4 Enhancement of gamma-aminobutyric acid by environmental stresses stimulation Gamma-aminobutyric acid concentration increases under multiple hypoxia-specific environmental stress conditions, such as in the study by Deewatthanawong et al. (2010) and as a signal to induce higher stress resistance in plants (Ramesh et al., 2015; Shelp et al., 2012). Additionally, it was shown that GABA accumulation increased under stress conditions, such as cold shock and mechanical stimulation

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(Wallace et al., 1984). Salt stress was also reported to increase GABA content in rice leaves in the vegetative stage (Poonlaphdecha et al., 2012). Gamma-aminobutyric acid increases in dehulled rice after germination, especially under hypoxia. In a recent study, GABA accumulation was ultimately promoted after 60 h of germination, with the highest content being detected at 72 h in germinating brown rice under hypoxic condition (Ding et al., 2016). In this study, the GABA accumulation was genotype-specific under both normoxic and hypoxic condition. Regarding GABA production, Xianhui 207 rice was more responsive to the germination process than Heinuo rice, whereas Heinuo was more responsive to hypoxia than Xianhui 207 (Ding et al., 2016). Hypoxic/anaerobic conditions increased GABA levels, and also markedly increased polyphenol levels and antioxidant capability, wherein three phenolic acids: ferulic, p-coumaric, and sinapic acids, showed the largest increase (Shen et al., 2015). Sonication can be used as a form of physical energy for stimulating seeds to increase the levels of health-promoting compounds, including primary and secondary metabolites in plant-based foods (Hasan et al., 2017). Soaking of soybeans in water at 25 C and subsequent treatment in an ultrasonic bath (300 W, 40 kHz, 0.35 W/cm2) for 30 min enhanced GABA levels by 43.39% after 5 days of germination, compared with the untreated sample (Yang et al., 2015). Ultrasound treatment for 5 and 30 min after soaking increased GABA levels in 72 h-germinated soft white wheat by 10.26% and 30.69%, respectively (Ding et al., 2018a). Gammaaminobutyric acid level in red rice increased considerably after 72 h of germination, and then exhibited a further increase after treatment with power ultrasound at different stages during germination. The GABA content in red rice increased substantially after germination for 72 h, to a level 15.4 times higher than that of the ungerminated rice (2.91 mg/100 g). A further increase in the GABA content could be observed in the ultrasound-treated samples, compared with the control germinated rice samples. The GABA level of the ultrasound-treated rice after soaking for 12 h was 72.07 mg/100 g, while that of the rice sonicated for 5 min after 66 h of germination was 75.82 mg/100 g (Ding et al., 2018b). Previous studies have shown that both hypoxic and ultrasonic treatment can significantly enhance GABA accumulation in sprouting rice. The genotype and sprouting stage affect the response to these stresses. Further studies are needed to understand how to apply these stresses during the industry production on germinated rice products, and what the effects of these stresses are on other nutritional functions and processing properties of germinated rice.

8.4

Development of gamma-aminobutyric acid-enriched rice products

8.4.1 Gamma-aminobutyric acid enriched rice-based staple foods The production of germinated rice includes several unit operations such as hulling, cleaning, soaking, sprouting, and drying. This general method has been widely used

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for producing sprouted grain-based staple foods and sprouted whole-grain flours. In recent years, a number of inventions focused on the development of new equipment for automatically producing germinated rice for human use: to facilitate filling, shelling, sprouting, drying, packaging, etc. The process flow diagrams for the production of germinated rice in a pilot study are shown in Fig. 8.5. Fig. 8.6 shows a GABA-enriched, dried, germinated red rice product developed in a previous laboratory-scale study. The nutrients in the raw red rice and 36 h/72 h-germinated red rice are tabulated in Table 8.3. Numerous germinated grain-based products have been developed in recent years. Among them, germinated rice is considered the most popular GABAenriched staple food in Asian countries and the United States, pictured as shown in Fig. 8.7. Technically, GABA enrichment during germination can be realized in the form of hulled rice and dehulled rice, although the process steps and end-product quality of these two types are different. The use of dehulled brown rice for enriching GABA is more common, as its process is relatively mature.

Figure 8.5 Process flow diagrams of germinated rice (Drawn by Bin Wang, Yuanyuan Fan, etc.).

Figure 8.6 Photographs of red rice (0 h) and 36 h/72 h-germinated red rice.

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Table 8.3 Nutrients levels in red rice and 36 h/72 h-germinated red rice Nutrients

Unit (DB)

0h

36 h

72 h

GABA Starch Crude protein Crude fat Ash Reduced sugar Soluble fiber Insoluble fiber

mg/100 g g/100 g g/100 g g/100 g g/100 g g/100 g g/100 g g/100 g

16.1 44.6 7.37 0.8 1.3 0.5 2.1 6.8

50.5 44.0 8.52 0.3 1.4 0.5 1.5 5.9

111.0 23.8 10.5 4.8 2.1 22.6 3.6 13.1

All samples were tested by SGS-CSTC Standards Technical Services Co. Ltd.; DB means dry basis.

Figure 8.7 Packaged germinated sprouted rice products available in the global market. A limited collection from Google Images on the market.

8.4.2 Gamma-aminobutyric acid enriched rice-based supplementary foods Rice-based supplementary foods include cereals, biscuits or cookies, rice tea, rice milk, rice cake, and other snacks prepared from grains. Gamma-aminobutyric

Development of gamma-aminobutyric acid
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acid
enriched rice could be used as an ingredient in the production of these grainbased foods. Table 8.4 lists various germinated rice products developed in Asia. Fig. 8.8 shows several GABA-enriched rice-based supplementary foods available in the global market. It is obvious that germinated rice products and GABA have gained more and more attention. The market of these new products continues to grow. In the future, the health benefits of these GABA-enriched rice-based supplementary foods need to be identified with more clinical study.

8.4.3 Production and evaluation standard for gammaaminobutyric acid
enriched germinated rice products Researchers in universities and food companies from different countries have currently filed a number of patents and developed different GABA-enriched germinated rice products. However, there is no standard method for the evaluation of the products. Most of the companies are still using the quality evaluation method of conventional rice products to evaluate GABA-enriched germinated rice products. The GABA concentrations in the GABA-enriched end-products can be measured and labeled on the package, which is displayed as a highlight nutrition feature. The level of GABA is regarded as a key factor to score these GABAenriched foods. Nevertheless, the content of other functional components and overall quality are also important for product evaluation. In addition, the balance of nutrition and the cost of enhancement process cost should be considered.

8.4.4 Future needs for gamma-aminobutyric acid
enriched germinated rice product development The whole-grain sprouted rice is the earliest type of GABA-enriched germinated rice product, having a history of more than 25 years in the food industry. Fifteen packaged products are shown in Fig. 8.7, including different types of pigment dehulled rice (brown rice, red rice, black rice), cooked, and dried rice. Consumers always look for appealing attributes on new foods. Similarly, new sprouted rice products should highlight the health benefits, with features likely to be or contain whole grain, GABA, gluten-free, sprouted, organic, etc. The sale price and the conveniences for cooking are also be considered. Research and development (R & D) activities of GABA-enriched germinated rice flour, as a new addition in the grain-based products market, are expected to find more applications in bread, cereal, beverage, rice tea, etc., as shown in Fig. 8.8 and Table 8.4. The production of rice-based ingredients with improved nutrition and flavor is expected to become the focus in the development of new germinated rice products.

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Table 8.4 Applications of germinated rice in foods based on the Google patents data base: A limited collection Type of products

Grain ingredients

Patent

High GABA germinated brown rice High GABA germinated brown rice tea High GABA germinated rice milk Infant-use nutritional rice flour A kind of vinegar A kind of grain beverage A kind of crisp Germinated brown rice cake Selenium-enriched germinated grain food Extracted antioxidant peptide Nutritional supplement use for delaying aging A kind of healthcare flour

Brown rice Brown rice Brown rice Brown rice Brown rice Brown rice Brown rice Brown rice Brown rice Brown rice Brown rice, corn

CN102835630 CN102919470 CN104171979 CN104222797 CN104212698 CN104223303 CN104186618 CN104186617 CN104041764 CN103468777 CN104026448

Brown rice, millet, barley Brown rice, buckwheat Black rice, red rice Brown rice, oat, black wheat, glutinous millet Brown rice, buckwheat, oat,

CN104273421

A kind of healthcare coarse grain food Yam-rice soup A kind of convenient coffee

Nutritious rice oatmeal used for reducing blood fat and preventing hyperglycemia Instant porridge Nutritional germinated cereals mix A kind of GABA-enriched germinated brown rice A kind of GABA-enriched cookie A kind of GABA-enriched crispy pancake A composite nutritional powder

A kind of nutritional instant rice Germinated brown rice yoghourt GABA-enriched fermented food GABA-enriched brown rice product Alcoholic drinks containing GABA Cut germination rice

CN104222769 CN103461908 CN103493945

CN103876046

Sorghum, rice Tartary buckwheat, oats, brown rice Brown rice

CN104207018 CN104222777

Brown rice Brown rice

CN105580875 CN105053111

Wheat germ and germinated brown rice Germinated brown rice, roasted black rice Germinated brown rice Sprouted brown rice bran Giant germ rice, brown rice Germinated brown rice Germinated 50% polished rice

CN102669580

CN101283754

CN101984852 CN101077092 JP2005052103A JP4082989B2 KR100857195B1 KR100970227B1

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Figure 8.8 GABA enriched rice-based supplementary foods available in the global market. A limited collection from Google Images.

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